Unraveling the Energetics and Dynamics of Atom-Radical and Radical-Radical Reactions of Atomic Silicon and Silylidyne Radicals with Main Group Hydride Radicals

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With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Professor Ralf I. Kaiser of the University of Hawaii is using crossed molecular beam experiments to study elementary atom-radical and radical-radical reactions of the simplest silicon-containing open shell reactants with prototype second row main group hydride radicals forming small silicon-bearing molecules under single collision conditions. These experiments are exceptionally challenging since they target previously unstudied bimolecular reactions of two open-shell transients involving the refractory element silicon. Professor Kaiser and his students will investigate the energy-dependent chemical dynamics of the bimolecular atom-radical and radical-radical reactions under single collision conditions utilizing a state-of-the-art, ultra-clean crossed molecular beam machine. The experimental results will be merged with ab initio and quasi classical trajectory calculations in collaboration with Professor Martin Head-Gordon (University of California, Berkeley). This study will provide excellent opportunities for the training of graduate and undergraduate students including women, veterans, along with indigenous Hawaiians and Pacific Islanders, thus encouraging students to do hands-on research in reaction dynamics and preparing them for leadership positions in education and research. This project benefits society by incorporating outreach activities through the organization of a symposium on silicon chemistry, broadening the participation of underrepresented minorities, and enabling educators to incorporate research activities into school and college teaching.This project focuses on synergistic experimental and computational studies of elementary reactions of two open shell reactants comprising the simplest silicon containing species [atomic silicon (Si) and the silylidyne radical (SiH)] and second row main group hydride radicals [methylidyne (CH), amino (NH2), hydroxyl (OH)]. The significance of this project is that our study provides new knowledge on the exotic main group silicon chemistry at the molecular level leading to archetype dinuclear silicon-bearing diatomics [SiE; E = C, N, O] along with their hydrogenated counterparts, of which many have been only predicted to exist theoretically. The results will also provide insight intol the underlying chemical dynamics and reaction mechanisms, expose the chemical bonding and molecular structure of small silicon-bearing systems, and provide a framework for considering silicon-based molecules as molecular building blocks of, for example, silicon carbide and silicate nanoparticles in the interstellar medium. These studies may change our perception on the concepts of chemical bonding, reactivity, and electronic structure of silicon in small molecules and how they compare to the isovalent carbon counterparts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.